However, in my defense, I recently picked it up again and am still enjoying it. It got me thinking ("Uh oh," you say, "I'm in for a long read here." Well.. maybe).
The book of Genesis tells us that God created man [i.e., humankind] "in His image." That is, God image-d part of Himself in the male-and-female-ness of humanity. As Popcak says, it's stamped on our very bodies. Furthermore, when he talks about "sexuality" he's talking about "how we communicate ourselves to others and use our bodies to work for the good of others" (p 68). And so, the theology (the study of God) of the body has primarily to do with how we relate to God in and through and with our bodies.
We obviously relate directly to and with God (worship, prayer, etc) and we do this with our bodies by means of the sacraments. But we also have a relationship with God through our fellow beings (it is not good for man to be alone). How do we relate to other humans with our bodies? The obvious answer (and the most profound example) is the "marital embrace." But what I've been thinking about lately is all the infinite other ways we relate to people with our bodies. Because of our unique sexuality (remember, that's our whole-body-ness) we are called to love like God loves, using our bodies. And we're not only called to love our spouse as God does, but everyone.
Love between a husband and wife has to be free (no one's forcing the Love), total (no reservation or lies), faithful (no cheating!), and fruitful (open to children). As I've been reading Popcak's book I've realized that we are called to that kind of Love in every aspect of our lives. I know--you're probably thinking, "How can my 'love' for So-and-So be fruitful if we're not married, or even the same gender?" I asked the same question :) But we can all be "pro-creative;" that is, we can bring new life to the world in many different ways, not just biologically. If your encounters with your fellow beings are positive and uplifting and sincerely Charitable (as in Love), you can communicate God's life-giving Love to them.
I clearly haven't sorted this all out yet (nor have I finished the book). But it's getting me excited. I know the goodness of authentic married Love, and I'm positively giddy at the idea of being able to share that Love--the same Love, that is, not by the same means ;)--with others I encounter. Isn't that exciting?